Bottom Line:
Gas transport mechanisms that characterize the hermetic behavior of MEMS packages are fundamentally different depending upon which sealing materials are used in the packages.In metallic seals, gas transport occurs through a few nanoscale leak channels (gas conduction) that are produced randomly during the solder reflow process, while gas transport in polymeric seals occurs through the bulk material (gas diffusion).In this review article, the techniques to measure true leak rates of MEMS packages with the two sealing materials are described and discussed: a Helium mass spectrometer based technique for metallic sealing and a gas diffusion based model for polymeric sealing.

ABSTRACTGas transport mechanisms that characterize the hermetic behavior of MEMS packages are fundamentally different depending upon which sealing materials are used in the packages. In metallic seals, gas transport occurs through a few nanoscale leak channels (gas conduction) that are produced randomly during the solder reflow process, while gas transport in polymeric seals occurs through the bulk material (gas diffusion). In this review article, the techniques to measure true leak rates of MEMS packages with the two sealing materials are described and discussed: a Helium mass spectrometer based technique for metallic sealing and a gas diffusion based model for polymeric sealing.

Mentions:
The original fringe pattern of the specimen before pressurization is shown in Figure 10(a). A carrier pattern of constant displacement gradient is added to the original pattern by a small rigid body rotation of the specimen; the number of carrier fringes over the cavity was about 20 which was equivalent to 6.3 μm. The modulated pattern is shown in Figure 10(b). After the two-dimensional FFT, the real harmonic is isolated in the frequency domain [Figure 10(c)]. The center of the spectrum is moved to the origin of the frequency axis to remove the carrier frequency in the frequency domain. Then, the inverse Fourier transform is performed to restore the original phase map [Figure 10(d)]. Unwrapping of this phase map yields a fractional fringe orders with high fidelity at every point. This information is used to generate a 3D deformation map shown in Figure 10(e). The configuration used in the experiment offered the displacement measurement resolution of ±15 nm and the pressure regulation accuracy of ±0.3 psi (±0.02 atm).

Mentions:
The original fringe pattern of the specimen before pressurization is shown in Figure 10(a). A carrier pattern of constant displacement gradient is added to the original pattern by a small rigid body rotation of the specimen; the number of carrier fringes over the cavity was about 20 which was equivalent to 6.3 μm. The modulated pattern is shown in Figure 10(b). After the two-dimensional FFT, the real harmonic is isolated in the frequency domain [Figure 10(c)]. The center of the spectrum is moved to the origin of the frequency axis to remove the carrier frequency in the frequency domain. Then, the inverse Fourier transform is performed to restore the original phase map [Figure 10(d)]. Unwrapping of this phase map yields a fractional fringe orders with high fidelity at every point. This information is used to generate a 3D deformation map shown in Figure 10(e). The configuration used in the experiment offered the displacement measurement resolution of ±15 nm and the pressure regulation accuracy of ±0.3 psi (±0.02 atm).

Bottom Line:
Gas transport mechanisms that characterize the hermetic behavior of MEMS packages are fundamentally different depending upon which sealing materials are used in the packages.In metallic seals, gas transport occurs through a few nanoscale leak channels (gas conduction) that are produced randomly during the solder reflow process, while gas transport in polymeric seals occurs through the bulk material (gas diffusion).In this review article, the techniques to measure true leak rates of MEMS packages with the two sealing materials are described and discussed: a Helium mass spectrometer based technique for metallic sealing and a gas diffusion based model for polymeric sealing.

ABSTRACTGas transport mechanisms that characterize the hermetic behavior of MEMS packages are fundamentally different depending upon which sealing materials are used in the packages. In metallic seals, gas transport occurs through a few nanoscale leak channels (gas conduction) that are produced randomly during the solder reflow process, while gas transport in polymeric seals occurs through the bulk material (gas diffusion). In this review article, the techniques to measure true leak rates of MEMS packages with the two sealing materials are described and discussed: a Helium mass spectrometer based technique for metallic sealing and a gas diffusion based model for polymeric sealing.